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A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Particle Processes".

Deadline for manuscript submissions: closed (15 August 2023) | Viewed by 31924

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Dr. Jan Havlík

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Faculty of Mechanical Engineering, Czech Technical University in Prague, Technicka 4, 16607 Prague, Czech Republic
Interests: energy conversion; drying technology; waste heat recovery; heat exchangers; biomass drying; heat transfer; condensation

Special Issue Information

Dear Colleagues,

Drying and dewatering processes are frequently used for treating many different types of materials before their further use or final consumption. The drying of solids is one of the most common unit operations found in diverse processes such as those used in the agricultural, energy, food, chemical, pharmaceutical, pulp and paper, polymer, ceramic, mineral, and textile industries. As the drying process is an intensive and energy-consuming operation, any improvements in the existing dryer design and any reductions in cost will be beneficial to the industry.

The main factors to focus on in current drying and dewatering research are the intensification of the process, the improvement of the quality of the dried product, and the reduction of the energy intensity of the process and environmental issues while ensuring high final product quality. Therefore, for the reliable design of new drying and dewatering systems, it is important to establish a good understanding of the process and the underlying mechanisms.

The aim of this Special Issue is to identify and review the current knowledge and new trends in drying and dewatering techniques. Both experimental and modelling approaches to the design of novel drying and dewatering systems are welcome.

Advanced drying and dewatering processes include the application of drying in new industrial fields, indirect drying, fluidized bed drying, superheated steam drying, and other modern methods, including their integration into industrial systems and heat recovery systems.

Topics include, but are not limited to, applications in the following areas:

Novel drying and dewatering technologies and solutions;
Mathematical modelling and simulation of drying process;
Process intensification;
Energy efficiency of drying and energy saving;
New trends in design of dryers;
Environmental issues.

Dr. Jan Havlík
Guest Editor

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Keywords

drying and dewatering
modelling and simulation of drying process
process intensification
energy efficiency
environmental issues

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Published Papers (11 papers)

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Research

19 pages, 4075 KiB

Open AccessFeature PaperArticle

Impact of Pulsed Electric Field Treatment on the Process Kinetics and Selected Properties of Air and Dehumidified Air-Dried Mushrooms

by Magdalena Dadan, Alicja Barańska, Aleksandra Matys, Katarzyna Rybak, Dorota Witrowa-Rajchert, Artur Wiktor and Małgorzata Nowacka

Processes 2023, 11(7), 2101; https://doi.org/10.3390/pr11072101 - 14 Jul 2023

Cited by 4 | Viewed by 1158

Abstract

The study examined the effects of pulsed electric field treatment on the kinetics and properties of convective-dried mushrooms using different drying agents. Increasing the drying air temperature reduced drying time, while the use of dehumidified air resulted in faster water removal. PEF treatment, depending on the parameters, shortened the drying time maximum by 12% or extended the drying time. The physical (dry matter content, rehydration properties, hygroscopic properties, and color) and chemical (polyphenols content and anti-oxidant activity) properties were analyzed. The dry matter contents of the mushrooms were influenced by the drying temperature, while PEF pre-treatment did not influence the rehydration and hygroscopic properties in both cases of drying using air humidity. However, the color parameters were affected by the drying method and energy input, with higher energy input leading to decreased lightness, increased redness, and color saturation. The chemical analyses revealed that the anti-oxidant compounds in the dried mushrooms were influenced by various factors, with PEF treatment and drying non-dehumidified air polyphenol content increasing, whereas dehumidified air caused more phenolic degradation if it was combined with PEF treatment. Anti-oxidant activity varied depending on the drying agent, with non-dehumidified air generally exhibiting better properties. The highest total polyphenol content and best anti-oxidant properties were obtained for the PEF pre-treated with 3 kJ/kg of energy and dried with non-dehumidified air at a temperature of 70 °C. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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14 pages, 25311 KiB

Open AccessArticle

Dried Droplets of Diluted Blood to Detect a High Concentration of Lipids

by Monserrat Ancheyta-Palacios, Iris G. Velasco-Terán, Yojana J. P. Carreón and Jorge González-Gutiérrez

Processes 2023, 11(7), 2047; https://doi.org/10.3390/pr11072047 - 9 Jul 2023

Cited by 2 | Viewed by 2445

Abstract

Hyperlipidemia is the elevated concentration of lipids in the blood, and it increases the probability of arterial obstruction, infarctions, and other complications of the circulatory system. While there are indications that qualitative analysis of blood stains could potentially identify patients with this pathology, the efficacy of this method remains uncertain. In this paper, we report an experimental study that investigates the formation of patterns in dried blood droplets with varying concentrations of ultrapure water. Two blood samples, one healthy and one with moderate hyperlipidemia, were examined to determine the ideal water and blood mixtures for detecting high lipid concentrations. Numerous intricate patterns were observed throughout the central region and periphery of the dried droplet. These patterns encompass various forms, such as plaques, bump-like patterns, and a range of cracks including random, radial, and ortho-radial configurations. By calculating the entropy of the Gray Level Co-occurrence Matrix (GLCM) and analyzing ROC curves, we determined that solutions with 4% and 12% hematocrit (indicating a high percentage of ultrapure water) exhibit over 95% accuracy in differentiating high lipid concentrations. These findings provide a promising outlook for the development of diagnostic methods based on the study of diluted blood coatings. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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28 pages, 16140 KiB

Open AccessArticle

Effect of Drying Pretreatment on Cellulolytic Enzymatic Hydrolysis of Lignin from Napier Grass

by Syazmi Zul Arif Hakimi Saadon and Noridah Binti Osman

Processes 2023, 11(4), 1092; https://doi.org/10.3390/pr11041092 - 4 Apr 2023

Cited by 2 | Viewed by 1846

Abstract

Biomass can be a viable supplement and alternative to non-renewable sources of fuel and chemicals. Lignin is an important part of biomass sources which can be used in various chemical and fuel industries. This study explores the pretreatment of lignin from Napier grass using thermal and physical means, as well as extraction of lignin via cellulolytic enzymatic hydrolysis to determine the optimum condition for feedstock pretreatment. Napier grass parts under various drying conditions and particle sizes were treated with enzymes. Moisture analysis, FTIR spectroscopy, UV–Vis analysis, and Klason lignin were carried out to analyze the moisture, functional group, and yield of lignin. Moisture content of the samples were inversely proportional to the drying conditions. The FTIR result showed lower peak intensity for higher drying conditions, while ball-milling showed less reduction in peak intensity. More Klason lignin was extracted under higher drying conditions. The yield of cellulolytic enzymatic lignin (CEL) was found to be more than actual lignin content, suggesting cellulose was not fully degraded. The FTIR spectra of CEL was found to be closer to that of lignin, but purification was still needed. Optimization was carried out by evaluating the statistical significance of each pretreatment effect of the pretreatments. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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17 pages, 1404 KiB

Open AccessArticle

Hawthorn Drying: An Exploration of Ultrasound Treatment and Microwave–Hot Air Drying

by Mohammad Kaveh, Małgorzata Nowacka, Esmail Khalife, Kamal Imanian, Yousef Abbaspour-Gilandeh, Maryam Sabouri and Safoura Zadhossein

Processes 2023, 11(4), 978; https://doi.org/10.3390/pr11040978 - 23 Mar 2023

Cited by 6 | Viewed by 2140

Abstract

Drying is one of the methods used for preserving fruits and vegetables. However, due to the lengthy process and elevated temperature of convective drying, other pretreatment and drying methods are studied to shorten the drying time and obtain high-quality products. This study aimed to examine the effect of ultrasonic (US) pretreatment and microwave–hot air drying (MW–HA) on the drying time, specific energy (SEC), qualitative properties (e.g., color, shrinkage, and rehydration ratio), and bioactive compound properties (e.g., antioxidant activity, phenolic, and flavonoid contents) of hawthorn fruit. Experiments were performed using ultrasound pretreatment and a microwave dryer (microwave power: 180, 360, and 540 W) at air temperatures of 40, 55, and 70 °C. Drying of hawthorn lasts from 35 min for the ultrasound-treated sample (dried at 540 W and 70 °C) to 180 min (dried at 180 W and 40 °C without US treatment). The lowest amount of SEC (24.11 MJ/kg) was obtained using the US–MW–HA air drying method (dried at 540 W and 70 °C). The lowest values in total color change (13.37) and shrinkage (22.47%) were recorded for the sample dried with a MW power of 360 W and air temperature at 55 °C with US pretreatment prior to drying. Generally, the use of US and MW–HA air drying reduces the antioxidant activity (AC), total phenolic content (TPC), and total flavonoid content (TFC) during processing compared to fresh samples. The highest values for AA (28.01%), TPC (69.44 mg GAE/g d.m.), and TFC (64.38 mg QE/g) obtained at 360 W and 55 °C with US pretreatment for hawthorn fruit dried. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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16 pages, 1656 KiB

Open AccessArticle

Controlled Germination of Faba Beans: Drying, Thermodynamic Properties and Physical-Chemical Composition

by Lumara Tatiely Santos Amadeu, Alexandre José de Melo Queiroz, Rossana Maria Feitosa de Figueirêdo, João Paulo de Lima Ferreira, Wilton Pereira da Silva, Josivanda Palmeira Gomes, Yaroslávia Ferreira Paiva, Caciana Cavalcanti Costa, Henrique Valentim Moura, Dyego da Costa Santos, Ana Raquel Carmo de Lima and Hanndson Araujo Silva

Processes 2022, 10(8), 1460; https://doi.org/10.3390/pr10081460 - 26 Jul 2022

Cited by 4 | Viewed by 1837

Abstract

The objective of this work was to determine the drying kinetics and the thermodynamic properties of the drying process of germinated seeds from faba beans of the Olho-de-Vó Preta (OVP), Raio-de-Sol (RS) and Branca (B) varieties. Additionally, the physicochemical properties of the germinated seeds and subsequent dried flours were determined. A thin layer of seeds were dried using a convective dryer at temperatures of 50, 60, 70 and 80 °C. Mathematical models were applied to the drying experimental data. The samples were further characterized for water content, water activity, ash, pH, alcohol-soluble acidity, total and reducing sugars, proteins, and starch. Page and Midilli models revealed the best predictions of the drying kinetics for all evaluated conditions. The effective diffusion coefficient increased with increasing temperature and presented magnitude in the order of 10⁻⁹ m²/s. The activation energy presented results in the range of 19 and 27 kJ/mol, falling within the range reported for agricultural products. The entropy and enthalpy values were higher in the OVP, followed by RS, higher than in the B variety. The increase in drying temperature resulted in a reduction of enthalpy and entropy and an increase in Gibbs free energy, indicating that the drying process is endothermic and requires external energy. Samples have acidic pH and acidity decreased with drying; the RS and B varieties had higher sugar contents; the B variety had the highest protein contents, and these were obtained from the in natura germinated samples; in the B variety the highest starch content was obtained. All flours showed good characteristics, presenting themselves as an alternative for diversifying the supply of beans. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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17 pages, 2183 KiB

Open AccessFeature PaperArticle

Dehydration and Rehydration Kinetics Modeling in the Phytochemical, Aroma, and Antioxidant Capacity of Tree Tomato Fruit Dried with Microwaves and Freeze Driers: A Comparative Study

by Marc Antoine Ndisanze and Ilkay Koca

Processes 2022, 10(8), 1437; https://doi.org/10.3390/pr10081437 - 22 Jul 2022

Cited by 3 | Viewed by 2854

Abstract

In the present study, we investigated and compared the effect of microwaves and freeze-drying methods on the dehydration and rehydration kinetics in the phenolic, anthocyanin, aroma profiles, and antioxidant properties of tree tomato fruit (Solanum betaceum). The tree tomatoes were dried using microwaves at 350 W, 500 W, and 650 W, and then freeze-dried. The obtained drying curves were processed to find the most suitable mathematical modeling among the different moisture ratio expressions. Total phenolics, total anthocyanins, total flavonoids total carotenoids, vitamin C, Ferric Reducing Antioxidant Power (FRAP), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were tested. Using High performance Liquid Chromatography (HPLC), phenolic and anthocyanin compound profiles were identified. The aroma profile was analyzed using gas chromatography-MS. The Midilli model, among others, precisely describes the dehydration methodology of all used drying methods with the coefficient of determination R² = 0.99. On the other hand, the Weibull model precisely describes the rehydration process of the used drying methods (R² = 0.99). Physical changes (color, shrinkage) were also studied. The freeze-dried tree tomatoes had a high number of phenolic compounds with 3.94 ± 0.26 mg GAE/g and total carotenoid compounds with 0.48 ± 0.04 µg/g. Epicathechin was the most abundant compound among the tested phenolics, followed by Cathechin. The Pelargonidin-3-glucoside was the most abundant anthocyanin whereas in freeze-dried tree tomatoes, 1.22 ± 0.01 mg/g. Fifty-four aroma compounds were detected and quantified. Among others, Eucalyptol was one of the most abundant aroma compounds analyzed in dried tree tomato fruit. Freeze-dried tree tomatoes retained most of the antioxidant and flavor compounds analyzed. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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14 pages, 11550 KiB

Open AccessArticle

Experimental Study on a New Combined Gas–Liquid Separator

by Lei Ji, Qin Zhao, Huiming Deng, Lanyue Zhang and Wanquan Deng

Processes 2022, 10(7), 1416; https://doi.org/10.3390/pr10071416 - 20 Jul 2022

Cited by 3 | Viewed by 2531

Abstract

Gas–liquid separation at natural gas wellheads has always been a key technical problem in the fields of natural gas transportation and storage. Developing a gas–liquid separation device that is both universal and highly efficient is the current challenge. A new type of combined gas–liquid separation device was designed in this study, and the efficiency of the separator was studied using a laser Doppler anemometer and phase Doppler particle analyzer at a flow rate of 10–60 Nm³/h. The results showed that the separation efficiency of the combined separator was above 95% at each experimental flow rate, verifying the strong applicability of the combined separator. Moreover, the separation efficiency was as high as 99% at the flow rates of 10 and 60 Nm³/h, thereby realizing efficient separation. This study is significant to the development of gas–liquid separation devices. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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18 pages, 5523 KiB

Open AccessArticle

Hierarchical Exploration of Drying Patterns Formed in Drops Containing Lysozyme, PBS, and Liquid Crystals

by Anusuya Pal, Amalesh Gope and Germano S. Iannacchione

Processes 2022, 10(5), 955; https://doi.org/10.3390/pr10050955 - 11 May 2022

Cited by 8 | Viewed by 3029

Abstract

Biological systems, by nature, are highly complex. These systems exhibit diverse hierarchical spatial and temporal features when driven far from equilibrium. The generated features are susceptible to the initial conditions that largely depend on vast parameter space. Extracting information on their properties and behavior thus becomes far too complex. This work seeks to examine the drying kinetics of the drops containing a globular protein (lysozyme (Lys)), phosphate buffer saline (PBS), and thermotropic liquid crystal (LCs). The drying evolution and the morphological crack patterns of these drops are examined using high-resolution microscopy, textural image analysis, and statistical methods. This study observes that the textural parameters can identify the (i) phase separation of the salts present in the PBS and (ii) the LCs’ birefringence during the drying evolution. This birefringence activities of the LCs slow down when the initial PBS concentration is increased from 0.25 to 1× despite using a fixed volume of LCs. To comprehend such a surprising effect, the combinations of (i) Lys+PBS and (ii) PBS+LCs are thoroughly examined. A phase diagram is established as a function of initial concentrations of Lys and PBS. The scanning electron microscopic images of Lys+PBS reveal that the tuning between lysozyme and salt concentrations in PBS plays a significant role in determining the morphological patterns. The Lys drops with and without LCs exhibit two distinct regions: the peripheral ring (“coffee-ring”) and the central ones. This phase-separated ring formation indicates that the film containing Lys and salts might have formed on top of these LCs in the central region, which reduces the optical response (birefringence) of LCs. A physical mechanism is proposed in this paper to anticipate the redistributions of LCs in a multi-component system such as Lys+PBS+LCs. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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11 pages, 3865 KiB

Open AccessFeature PaperArticle

Drying Biomass with a High Water Content—The Influence of the Final Degree of Drying on the Sizing of Indirect Dryers

by Jan Havlík, Tomáš Dlouhý and Ján Pitel’

Processes 2022, 10(4), 739; https://doi.org/10.3390/pr10040739 - 11 Apr 2022

Cited by 9 | Viewed by 4197

Abstract

This article deals with the influence of the final drying degree of moist biomass used as fuel in a power or CHP plant on indirect dryer sizing. For a description of the drying process, experiments with wet bark containing approx. 50 wt% of water were carried out in a laboratory indirect dryer. A new parameter called drying effectivity was introduced, whose size varies according to the degree of biomass being dried. Its maximum value corresponds to the optimal biomass drying, when the relative size of the indirect dryer to evaporate the required mass of water from the biomass would be smallest. Based on the experimentally determined drying characteristics of wet bark, the optimal drying of 13 wt% of water content was evaluated. If the bark was dried to a lower water content, the required relative size and price of the dryer would increase. Similarly, drying a bark with water content above 31 wt% is not very advantageous because drying effectivity continues to increase rapidly at this stage, and the required relative size of the dryer therefore decreases. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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15 pages, 1584 KiB

Open AccessArticle

Effect of Drying Methods and Processing Conditions on the Quality of Curcuma longa Powder

by Sandra M. Llano, Ana María Gómez and Yudy Duarte-Correa

Processes 2022, 10(4), 702; https://doi.org/10.3390/pr10040702 - 5 Apr 2022

Cited by 11 | Viewed by 5648

Abstract

Turmeric (Curcuma longa) is a spice that has been used for a long time in traditional medicine for its anti-inflammatory properties and recently used in the food industry for its dyeing and flavoring properties. This work studied the effect of different drying methods (convection oven drying, fluidized bed drying, and traditional solar drying) on the quality of Curcuma longa powder. The effect of UV radiation on turmeric powder using different packaging materials (glass, aluminum foil bag, and low-density polyethylene bag), was also studied. Subsequently, the fluidized bed drying method was used to evaluate the effect of drying temperature. The results show that convection and fluidized bed drying had no significant impact on turmeric quality. However, solar drying degraded curcuminoids by 36.5% and the ORAC value decreased by 14%. Regarding the packaging materials, the aluminum bag prevented the deterioration of 14% of the curcuminoids for the powder exposed to UV radiation. Finally, the effect of temperature on fluidized bed drying was evaluated at 50–80 °C, finding that there were no significant differences in the curcuminoid content and antioxidant capacity of turmeric powder. This implies that the range of temperature used in this study is appropriate for drying this material using fluidized bed drying, producing a turmeric powder with a high content of bioactive compounds, when compared to convection oven and solar drying. Therefore, the turmeric powder obtained in this way can be used as an active ingredient in the formulation of different kinds of foods and supplements. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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14 pages, 2784 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Knudsen Diffusion and the Dusty Gas Approach for the Modeling of the Freeze-Drying Process of Bulk Food Products

by Patrick Levin, Moritz Buchholz, Vincent Meunier, Ulrich Kessler, Stefan Palzer and Stefan Heinrich

Processes 2022, 10(3), 548; https://doi.org/10.3390/pr10030548 - 11 Mar 2022

Cited by 3 | Viewed by 2724

Abstract

Freeze-drying is generally used to achieve high quality products and preserve thermal sensitive components; however, it is also considered as a high energy and costly process. Modeling of the process can help to optimize the process to reduce these drawbacks. In this work, a mathematical model is presented to predict the heat and mass transfer behavior for freeze-drying of porous frozen food particles during freeze-drying to optimize the process. For the mass transfer, a comparison between Knudsen diffusion and the more complex dusty-gas approach is performed. Simulation results of a single particle are validated by experiments of single-layer drying to extend the usage of this model from a single particle to a particle bed. For the moisture transfer, adaption parameters are introduced and evaluated. A comparison shows a good agreement of the model with experimental results. The results furthermore suggest a strong correlation of the drying kinetics with pore size and particle porosity. An increase in the pore diameter strongly improves the overall mass transfer rates and hence is a suitable parameter for an effective increase of the drying rates in freeze-drying. Full article

(This article belongs to the Special Issue Advanced in Dewatering and Drying Processes)

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